Compiling Linker undefined reference

[jestem pro]

Hello. I tried to compile my source but I get errors.
In tile.h I changed:

virtual ReturnValue __queryAdd(int32_t index, const Thing* thing, uint32_t count,
           uint32_t flags) const;

to:

    virtual ReturnValue __queryAdd(int32_t index, const Thing* thing, uint32_t count,
           uint32_t flags, Creature* actor = NULL) const;

(added Creature* actor = NULL)
I made the same with queryRemove.
And I get these errors:
[Linker error] undefined reference to `Tile::__queryAdd(int, Thing const*, unsigned int, unsigned int) const'
[Linker error] undefined reference to `Tile::__queryRemove(Thing const*, unsigned int, unsigned int) const'

In tile.cpp I added Creature* actor too. I don't exactly know what it means.
Thanks